1. Field of the Invention
This invention relates to an apparatus for conveying a sheet such as an original and at the same time, reading images such as characters formed on the sheet. An apparatus of this type is often used, for example, in a facsimile apparatus or the like.
2. Related Background Art
An apparatus of this type is disclosed, for example, in U.S. Pat. No. 4,438,918. In this apparatus, a sheet (an original) is conveyed along a predetermined conveyance path by conveying rollers. A slit is provided in the course of the conveyance path, and a light is applied to the original through the slit and the reflected light therefrom is imaged on an image sensor by a lens to thereby read the image of the original. The image sensor comprises a photoelectric conversion element disposed on a base plate widthwise of the original, and the light reflected from the original is received and converted into an electrical signal by the photoelectric conversion element.
In such an apparatus, however, the image sensor can be disposed at a location within the apparatus into which it is difficult for outside light to enter, but a lens, a reflecting mirror, etc. are required, and this leads to bulkiness of the apparatus.
So, the assignee of the present invention has developed a reading apparatus for reading the image of an original directly by an image sensor without the use of a lens, a reflecting mirror, etc. In this reading apparatus, a photoelectric conversion element is provided on a transparent plate disposed on a base plate having a hole for passing therethrough the light beam from a light source, and the photoelectric conversion element is covered with a protective transparent sheet. When the original is to be read, the reflected light of said light beam applied to the original, which is being conveyed while contacting said protective transparent sheet, is received and converted into an electrical signal by the photoelectric conversion element.
In this reading apparatus, however, only the protective transparent sheet lies between the photoelectric conversion element and the sheet conveyance path and therefore, outside light which has entered into the sheet conveyance path through the inlet and/or the outlet for the sheet readily enters the photoelectric conversion element. Particularly, part of the outside light enters the element through the side edge surfaces of the transparent plate and the protective transparent sheet and provides a disturbing light, and this has led to the problem that such light appears as a noise signal in the photoelectric conversion element.
There has also been the problem that if the photoelectric conversion element is always exposed to the outside light, the element deteriorates more rapidly than otherwise.